tracing: Parse filter from boot event string

Make it possible to specify a trace event filter from the
kernel command line.

Example:

	trace_event=syscalls:sys_enter_clock_nanosleep:filter:which_clock==0

Link: https://patch.msgid.link/20260908-tracing-cli-event-filter-v2-7-05396a3fb663@linutronix.de
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 45 insertions, 13 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 31718ef337dc..26390e06969e 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -2511,5 +2511,6 @@ static inline int rv_init_interface(void)
 #endif /* _LINUX_KERNEL_TRACE_H */
 
 #if IS_ENABLED(CONFIG_KUNIT)
-void ftrace_parse_event_string(char *buf, char **match, char **sub, char **event, char **mod);
+void ftrace_parse_event_string(char *buf, char **match, char **sub, char **event, char **mod,
+			       bool handle_filter, char **filter);
 #endif
diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 5da0a8bbb110..6ba70dac1f06 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -94,7 +94,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
 			continue;
 		}
 
-		if (ftrace_set_clr_event(tr, buf, 1) < 0)
+		if (ftrace_set_clr_event(tr, buf, 1, false) < 0)
 			pr_err("Failed to enable event: %s\n", p);
 	}
 }
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index b27599c7d55d..a1ac2a02f4e2 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1458,10 +1458,21 @@ static int __ftrace_set_clr_event(struct trace_array *tr, const char *match,
 }
 
 VISIBLE_IF_KUNIT void
-ftrace_parse_event_string(char *buf, char **match, char **sub, char **event, char **mod)
+ftrace_parse_event_string(char *buf, char **match, char **sub, char **event, char **mod,
+			  bool handle_filter, char **filter)
 {
 	*event = NULL;
 	*sub = NULL;
+	*filter = NULL;
+
+	/* event filters can be appended with :filter:<filter> */
+	if (handle_filter) {
+		*filter = strstr(buf, ":filter:");
+		if (*filter) {
+			**filter = '\0';
+			*filter += 8;
+		}
+	}
 
 	/* Modules events can be appended with :mod:<module> */
 	*mod = strstr(buf, ":mod:");
@@ -1501,9 +1512,9 @@ ftrace_parse_event_string(char *buf, char **match, char **sub, char **event, cha
 }
 EXPORT_SYMBOL_IF_KUNIT(ftrace_parse_event_string);
 
-int ftrace_set_clr_event(struct trace_array *tr, const char *arg_buf, int set)
+int ftrace_set_clr_event(struct trace_array *tr, const char *arg_buf, int set, bool handle_filter)
 {
-	char *event, *sub, *match, *mod;
+	char *event, *sub, *match, *mod, *filter;
 
 	if (!tr)
 		return -ENOENT;
@@ -1512,9 +1523,9 @@ int ftrace_set_clr_event(struct trace_array *tr, const char *arg_buf, int set)
 	if (!dupped_buf)
 		return -ENOMEM;
 
-	ftrace_parse_event_string(dupped_buf, &match, &sub, &event, &mod);
+	ftrace_parse_event_string(dupped_buf, &match, &sub, &event, &mod, handle_filter, &filter);
 
-	return __ftrace_set_clr_event(tr, match, sub, event, set, mod, NULL);
+	return __ftrace_set_clr_event(tr, match, sub, event, set, mod, filter);
 }
 
 /**
@@ -1596,7 +1607,7 @@ ftrace_event_write(struct file *file, const char __user *ubuf,
 		if (*parser.buffer == '!')
 			set = 0;
 
-		ret = ftrace_set_clr_event(tr, parser.buffer + !set, set);
+		ret = ftrace_set_clr_event(tr, parser.buffer + !set, set, false);
 		if (ret)
 			goto out_put;
 	}
@@ -4865,10 +4876,10 @@ static __init void __early_set_events(struct trace_array *tr, char *buf, bool en
 	while ((token = strsep(&buf, ","))) {
 		if (*token) {
 			if (enable) {
-				if (ftrace_set_clr_event(tr, token, 1))
+				if (ftrace_set_clr_event(tr, token, 1, true))
 					pr_warn("Failed to enable trace event: %s\n", token);
 			} else {
-				ftrace_set_clr_event(tr, token, 0);
+				ftrace_set_clr_event(tr, token, 0, true);
 			}
 		}
 
diff --git a/kernel/trace/trace_events_test.c b/kernel/trace/trace_events_test.c
index 515d2e668c31..4a2d77fa0f58 100644
--- a/kernel/trace/trace_events_test.c
+++ b/kernel/trace/trace_events_test.c
@@ -8,7 +8,7 @@
 struct parse_event_string_test_case {
 	const char *input;
 
-	const char *match, *sub, *event, *mod;
+	const char *match, *sub, *event, *mod, *filter;
 };
 
 static const struct parse_event_string_test_case parse_event_string_test_cases[] = {
@@ -38,6 +38,12 @@ static const struct parse_event_string_test_case parse_event_string_test_cases[]
 		.event	= "event",
 	},
 	{
+		"sub:event:filter:filter",
+		.sub	= "sub",
+		.event	= "event",
+		.filter	= "filter",
+	},
+	{
 		"match",
 		.match	= "match",
 	},
@@ -51,6 +57,19 @@ static const struct parse_event_string_test_case parse_event_string_test_cases[]
 		.event	= "event",
 		.mod	= "module",
 	},
+	{
+		"sub:event:mod:module:filter:filter",
+		.sub	= "sub",
+		.event	= "event",
+		.mod	= "module",
+		.filter	= "filter",
+	},
+	{
+		"sub:event:mod:module:filter:unexpected-filter",
+		.sub	= "sub",
+		.event	= "event",
+		.mod	= "module:filter:unexpected-filter",
+	},
 };
 
 static void
@@ -72,18 +91,19 @@ KUNIT_ARRAY_PARAM(parse_event_string, parse_event_string_test_cases, parse_event
 static void parse_event_string(struct kunit *test)
 {
 	const struct parse_event_string_test_case *params = test->param_value;
-	char *input, *match, *sub, *event, *mod;
+	char *input, *match, *sub, *event, *mod, *filter;
 
 	input = kunit_kstrdup(test, params->input, GFP_KERNEL);
 	if (!input)
 		kunit_skip(test, "ENOMEM");
 
-	ftrace_parse_event_string(input, &match, &sub, &event, &mod);
+	ftrace_parse_event_string(input, &match, &sub, &event, &mod, params->filter, &filter);
 
 	EXPECT_NULL_OR_STR_EQ(test, match, params->match);
 	EXPECT_NULL_OR_STR_EQ(test, sub, params->sub);
 	EXPECT_NULL_OR_STR_EQ(test, event, params->event);
 	EXPECT_NULL_OR_STR_EQ(test, mod, params->mod);
+	EXPECT_NULL_OR_STR_EQ(test, filter, params->filter);
 }
 
 static struct kunit_case trace_events_test_cases[] = {